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jkornelis
May 25, 2005, 2:31 PM
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All I could find in the search was if you could off a static and dynamic. I was wondering if I could use a 9.4 and a 10.2 together.
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j_ung
May 25, 2005, 2:38 PM
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Absolutely, but rig your rap so you're pulling the 10.2, not the 9.4.
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chaps
May 25, 2005, 2:58 PM
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Here's an elaboration on j_ung's answer:
When you're rappelling on two different sized ropes, you have to be careful because they will feed through your rap device at different rates. The thicker the rope, the slower it goes through the device compared to the thinner rope. What this means, essentially, is that you're really rappelling on the thick rope and just using the thin rope to pull the thick one down. Here's an extreme example to make it clear:
Say you're rapping on a fat 11mm rope paired with dental floss. Tie them together at the top, thread them through the rings, etc. When you actually start to rap, you're really only placing weight on the thick rope. The floss is passing through your rap device, but it's not generating any friction compared to the thick rope.
So, as j_ung said, rig your rap so that the knot keeps the fat rope from slipping. Said another way: set it up so that you pull on the thin rope to get your ropes down.
I hope that isn't waaaaay too much explanation. I dealt with this question on a rap on Devils Tower last month and it took some thinking to understand.
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tenesmus
May 25, 2005, 3:26 PM
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This winter I ice climbed a lot with a friend who used a 9.8 for leading and carried a 7 for double rope rapping. He always tied them together with a sheep bend? He said it was the best knot for unequal diameter ropes.
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brolloks
May 25, 2005, 3:31 PM
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I think the two posts (j_ung and chaps)above are not explaining the same thing. The difference is on which side of the rap ring/anchor you leave the knot you used to tie the ropes together.
j-ung explains the way where the skinnier rope is the one passing through the rap ring (i.e. knot on the side of the fatter 10.2mm) After rapping, you will pull the 10.2 to get the ropes down, right? (knot will not pass through the anchor otherwise).
The other way is to have the thicker rope pass through the anchor, so you have to pull the skinny 9.4mm to get the ropes down.
Last case scenario can prove a problem if the skinny rope you're using isn't suitable for leading, and the thicker dynamic rope gets stuck out of reach while you're pulling the skinny to get the ropes back.... (hope I explain this clearly). You'll have to climb on your 9.4 to go and get the 10.2mm rope (if nothing seems to shake it loose).
If in your specific case you want to use a 9.4mm (as thinner diameter rope) and you can safely lead on it (i.e. it's dynamic), all the above haedaches don't apply to you. Just be careful, as chaps said. Thinner ropes pass quicker through a rap device - tie a safety knot, and watch those tail lengths to not rap off the end of the rope.
Be safe.
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zozo
May 25, 2005, 3:35 PM
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Just curious if you were to back up your rappel in this situation would you prussick around both lines still?
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chaps
May 25, 2005, 3:47 PM
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In reply to: Just curious if you were to back up your rappel in this situation would you prussick around both lines still?
I don't think that matters as much as going down. But, to be on the safe side, I'd prussick the lines just as I'd rapped them: if I was rapping on two, I'd prussick on two; if rapping on one, prussick on one.
It really shouldn't matter because a prussick will grab both lines and neither will move relative to the other. The trouble with rapping on different sized lines is that if it's set up incorrectly, the thin line can slide through the rap device without the rappeller being aware of it. If it's done wrong, you can rap off the end of the thin line and then fall to your death because there's no longer anything holding you to the anchors.
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brolloks
May 25, 2005, 3:53 PM
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To the original poster : are you talking about rappelling in general, or after climbing multi pitch?
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j_ung
May 25, 2005, 3:55 PM
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In reply to: Here's an elaboration on j_ung's answer: When you're rappelling on two different sized ropes, you have to be careful because they will feed through your rap device at different rates. The thicker the rope, the slower it goes through the device compared to the thinner rope. What this means, essentially, is that you're really rappelling on the thick rope and just using the thin rope to pull the thick one down. Here's an extreme example to make it clear: Say you're rapping on a fat 11mm rope paired with dental floss. Tie them together at the top, thread them through the rings, etc. When you actually start to rap, you're really only placing weight on the thick rope. The floss is passing through your rap device, but it's not generating any friction compared to the thick rope. So, as j_ung said, rig your rap so that the knot keeps the fat rope from slipping. Said another way: set it up so that you pull on the thin rope to get your ropes down. I hope that isn't waaaaay too much explanation. I dealt with this question on a rap on Devils Tower last month and it took some thinking to understand.
I think we actually differ on this one, gat :(. I'm saying rig the ropes the opposite way, because IMO, stuck ropes are more of a hazard. On walls that eat ropes, for example Devils Tower, anything you can do to minimize that danger is worth it, and a 9.4 has less chance of getting stuck than a 10.2. I get your point, also, but I'm not convinced that it's enough of an issue to worry about. I've rapped hundreds and hundreds of times on ropes rigged my way with zero problems.
To the OP: Correct me if I'm wrong, but I think your question was more about the safety of tying two different-diameter ropes together, no? There is some danger with wildly-varying diameters, but 9.4 and 10.2 isn't enough of a difference to worry about. It's AOK; use whatever knot you already use.
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j_ung
May 25, 2005, 3:56 PM
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In reply to: Here's an elaboration on j_ung's answer: When you're rappelling on two different sized ropes, you have to be careful because they will feed through your rap device at different rates. The thicker the rope, the slower it goes through the device compared to the thinner rope. What this means, essentially, is that you're really rappelling on the thick rope and just using the thin rope to pull the thick one down. Here's an extreme example to make it clear: Say you're rapping on a fat 11mm rope paired with dental floss. Tie them together at the top, thread them through the rings, etc. When you actually start to rap, you're really only placing weight on the thick rope. The floss is passing through your rap device, but it's not generating any friction compared to the thick rope. So, as j_ung said, rig your rap so that the knot keeps the fat rope from slipping. Said another way: set it up so that you pull on the thin rope to get your ropes down. I hope that isn't waaaaay too much explanation. I dealt with this question on a rap on Devils Tower last month and it took some thinking to understand.
I think we actually differ on this one, chaps :(. I'm saying rig the ropes the opposite way, because IMO, stuck ropes are more of a hazard. On walls that eat ropes, for example Devils Tower, anything you can do to minimize that danger is worth it, and a 9.4 has less chance of getting stuck than a 10.2. I get your point also, but I'm not convinced that it's enough of an issue to worry about. I've rapped hundreds and hundreds of times on ropes rigged my way with zero problems.
To the OP: Correct me if I'm wrong, but I think your question was more about the safety of tying two different-diameter ropes together, no? There is some danger with wildly-varying diameters, but 9.4 and 10.2 isn't enough of a difference to worry about. It's AOK; use whatever knot you already use.
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chaps
May 25, 2005, 4:04 PM
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In reply to: I think we actually differ on this one, chaps :(.
Bummer! Now I'll have to flame the heck out of you to prove to myself that I'm a better person, right? :lol: That stinks, 'cause I am NO good at flaming...
Is the size-difference-slippage really not an issue? From the people who were warning me about it, you'd think that it kills or injures thousands of people a year. OTOH, I've also seen the knot slide away from the anchors from normal rappelling motion when we were using two same-diameter ropes.
Perhaps the most important thing to remember is to tie knots in the ends of the ropes, lest you rap off the end of them.
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j_ung
May 25, 2005, 4:15 PM
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In reply to: Is the size-difference-slippage really not an issue? From the people who were warning me about it, you'd think that it kills or injures thousands of people a year. OTOH, I've also seen the knot slide away from the anchors from normal rappelling motion when we were using two same-diameter ropes.
I don't want to spout tech and test results that I don't have. But I do have some personal experience, which tells me that it isn't much of a problem. And in truth, if we tie knots in the ends like we should, I don't see how it can be a problem. Looks like we agree on that one!
In reply to: Perhaps the most important thing to remember is to tie knots in the ends of the ropes, lest you rap off the end of them.
Now as to which one of us is better... let's just flip a coin. I have one here. Call it. :P
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adamtd
May 25, 2005, 4:17 PM
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Let's put this debate to rest. When doing a double rope rappel with two different diameter ropes, you need to set it up so that you are pulling on the thinner line to retrieve your ropes. This is crucial for two reasons. First, as it was already stated, teh fatter the rope, teh greater the friction. With the greater friction on the fat rope, the thinner rope will pass through your delay/rappel evice faster. If the knot is on the wrong side of the anchor (on the fat side), your knot can actually follow you down the wall, making the your thin line in essence shorter, and your fat line longer. When you reach the end of the thin line, but you're still on teh fat line... you fall (that's bad).
Now for the second point. You need to retrieve your ropes by pulling on teh thin line. The thin line does not get hung up more than the fat rope, in fact it get's hung up more. Objects wall down and out from teh wall, unless acted upon by an outside force. On exposed rock, the force is usually wind, and you want all the weight and mass you can get to conteract teh forces the wind will place on the falling rope. Thin ropes can get blown into trees, flakes, and around horns much easier. (13 years of alpine, multi-pitch, and mountaineering have taught me this.)
For the record, I often climb with a 10.5 dynamic, and carry an 8mm static tag lien with me for the double rap rappel and other various uses. Yes you can't lead on the static line, but that's a chance I take. Often times, when I go to larger mountains or more remote ranges, I'll take multiple dynamic ropes because of teh chance I run of have a rope caught or chopped.
good luck and just use your head.
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j_ung
May 25, 2005, 4:25 PM
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Thanks adamtd, that's good info.
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phlsphr
May 25, 2005, 4:33 PM
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This may deserve a seperate thread, but I was interested in the following claim:
In reply to: On walls that eat ropes, for example Devils Tower, anything you can do to minimize that danger is worth it, and a 9.4 has less chance of getting stuck than a 10.2.
I admit that I don't have a lot of experience with thin ropes. But just sitting here thinking about it I can't see why a thick rope would be more prone to getting stuck than a fat one. If anything, wouldn't a thinner rope be MORE prone to slipping into cracks etc.? And wouldn't it be more prone to getting blown around? Anyhow, I'm not trying to pick a fight, I'm just wondering whether this is really so.
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paulraphael
May 25, 2005, 4:38 PM
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Some other thoughts on this:
1) you can safely tie ropes of wildly different diameters together. Alpinists routinely tie single lead ropes to skinny static trail lines, using and edk (parallel overhand knot). Extra care is required, though, especially if the ropes are wet or icy. Minimum of 30cm tails--45cm even better-- pulled tight on all four strands. you will be safer from the rope getting stuck than with any other knot.
2)In alpine and long multipitch situations where there's danger of ropes getting hung up from wind, pull the skinny rope. This also offers the advantage of having the knot on the skinny rope side of the anchor, which helps minimize rope slippage.
If there's no wind and you expect it to stay that way, pulling the thicker rope can be safer. I don't believe that a fat rope is more likely to get stuck than a skinny rope. If anything I think it's the opposite. However, pulling the fat rope, when there's no wind, gives you something you can lead up if something does get badly stuck.
And by the way, if there's a ton of wind (like enough that the ropes go up when you throw them down) don't rap. Lower the first climber.
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csproul
May 25, 2005, 4:39 PM
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I'll agree with adamtd about the way he is describing the skinny rope having less friction, knot moving ect...he has described it fairly well. But I think in most cases where people are using 9-10.5 ropes it is not much of an issue. And certainly where the OP is using a 9.4 and a 10.2 there is no issue. When doing multiple raps it is easier to alternate which side you are pulling so the first one down can start feeding the end to be pulled through the next rap anchor. That way it is already done when you are pulling the rope. Otherwise you'd have to feed the whole rope through or re-tie the ropes together to always have the same end pull. It would be worth it if using very different ropes or static/dynamic combinations.
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jkornelis
May 25, 2005, 4:43 PM
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So 10.2 will go through the rings. the knot will prevent much shifting of ropes. And learn the sheet bend knot. Has anyone ever had the knot get wedged in the rings?
Reason for question is for 3 person Multi pitching, lead with the 10.2, and follow with the 9.4. Then use both to rap off.
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davidji
May 25, 2005, 4:50 PM
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It's convenient if the thin line is the pull cord for the reasons stated above.
Often you want to alternate which side you pull though: multiple raps are faster if you feed the pull cord from one rap through the anchor on the next. There are several ways around the ropes moving at different speeds issue. As with other choices you make when rappelling, they have various benefits and risks. Here are a few choices:
Rap the thin line. Beware of sharp edges, and remember that the friction is going to reduce as you descend. If it's marginal at the top, fix it right away. I've rapped a single 6mm cord with a belay device, and an added friction setup. Not my first choice, but it works.
Have your partner prevent the slippage. It's really easy to do, from above or below. A stopper knot in the thin line is still a good idea.
Manage the slippage yourself. Tricky, although some people like this way. Good to have a stopper knot in the thin rope. Having the thin line a little longer than the thick one can help too.
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jkornelis
May 25, 2005, 4:52 PM
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I will have to practice it on a small rap, Thanks for all the help.
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j_ung
May 25, 2005, 5:11 PM
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In reply to: This may deserve a seperate thread, but I was interested in the following claim: In reply to: On walls that eat ropes, for example Devils Tower, anything you can do to minimize that danger is worth it, and a 9.4 has less chance of getting stuck than a 10.2. I admit that I don't have a lot of experience with thin ropes. But just sitting here thinking about it I can't see why a thick rope would be more prone to getting stuck than a fat one. If anything, wouldn't a thinner rope be MORE prone to slipping into cracks etc.? And wouldn't it be more prone to getting blown around? Anyhow, I'm not trying to pick a fight, I'm just wondering whether this is really so.
Well, to be honest, I think I'm beginning to be swayed... a little. adamtd spoke of his 8mm tag/rap rope, and in that case, I agree. But I've also been in a couple tight spots because fat ropes caught on the pull. Yes lighter ropes are more prone to being moved around by wind, but obstacles can also exist in the direct fall line of the rope. Fatter ropes produce more friction, but a thinner rope might slide into a crack easier.
Point being... There are a lot of things to consider on every rappel. For now, I'm going to stick with what I do, because it's been working for me for a long time. In high winds, though, I'm going to remember this thread and think before rigging.
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asandh
May 25, 2005, 5:14 PM
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:)
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j_ung
May 25, 2005, 5:33 PM
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In reply to: If safety and staying alive is your main concern when rapping with 2 different sized ropes, then the earlier explanation by "chaps" is the Correct One and "jungs explanation is wrong. If you do it Jung's way, it is possible that the thicker rope creates so much drag that the 2 ropes dramatically move in relation to one another and you find yourself rapping off the end of the thin rope long before you reach the end of the thick rope.
I'm curious how many people have experienced this phenomenon with ropes close to the diameters in the OP, 10.2 and 9.4. I rap on ropes of those thicknesses all the time and have never seen the ropes slip in relation to each other. But I have had problems rigging the other way.
Again, not arguing, just asking. I understand the theory, but does it actually happen?
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tradklime
May 25, 2005, 5:40 PM
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In reply to: And learn the sheet bend knot.
Forget the sheet bend, and learn the EDK.
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